This invention relates to a display device, and more particularly to a holographic optical waveguide display.
Optical waveguide devices are being developed for a range of display applications such as Head Mounted Displays (HMDs) and Heads Up Displays (HUDs). Another field of application of waveguides is in sensors such as eye trackers such as the ones disclosed in PCT Application No. PCT/GB2014/000197 entitled HOLOGRAPHIC WAVEGUIDE EYE TRACKER by Popovich et al and finger print sensors such as the ones disclosed in PCT/GB2013/000005 entitled CONTACT IMAGE SENSOR USING SWITCHABLE BRAGG GRATINGS by Popovich et al. However, waveguide devices that use total internal reflection (TIR) to transmit image information suffer from the problem the beam propagation may be disturbed by damage to or contamination of the external waveguide surfaces by foreign materials. There is a requirement for a waveguide display in which image light propagated within the waveguide is isolated from the external environment.